I know there is few Apple users here, yet never hurts to ask.
I own an ibook that has given me much love, other than the fact she will not run an Apple OS.
The machine will run any Linux distro, including Ubuntu. I installed Tiger, and I get the " you must shut down your computer " splash. tried several things including a new HDD. I then installed Leopard, same thing. The only thing I can think of, is an internal memory issue. The box contains 512 MB. I know there is a way to " shut off " certain areas of memory but they will be re- activated the next boot, so it would be useless. Any ideas will be entertained , thanks.